This invention relates to a method and a device for detecting foreign objects mixed in a liquid filling a transparent container.
It is necessary that the beer bottles filled with beer are detected as to whether foreign objects are mixed in the beer before their delivery. The foreign objects mixed in the beer are fungi, biomasses, fractions of rust, fractions of labels, etc. and have various sizes. Some of the foreign objects are as small as around 1 mm.phi., and others are as large as 10 mm.phi.. The foreign object detection for detecting such foregin objects with accuracy has been conducted visually by detectors, and the labor savings have been expected.
As a device for detecting defects of a bottle and foreign objects attached to the bottle has been known a bottle inspecting device in which a transmitted light image of a bottle is taken by a CCD camera, and, based on the transmitted light image, defects and foreign objects are detected. But the conventional bottle inspecting device is for detecting defects of an foreign objects in a bottle having few flaws on the outer surface, and has found it difficult to discriminate foreign objects mixed in a liquid in the bottle, such as a beer bottle, with a number of defects on the outer surface from the defects.
Thus conventionally it has been impossible to detect with high accuracy foreign objects in a liquid filling a transparent bottle with a comparatively large number of flaws on the outer surface.